This invention relates broadly to heat storage systems and particularly to systems for storing solar energy and recycled discharge heat.
As used herein, the terminology "heat storage unit" refers to an energy assembly of one or more cells which receives energy in the form of heat, stores this energy, and thereafter furnishes this energy in the form of heat upon demand therefor.
U.S. Pat. No. 4,127,161 to Clyne et al., describes an energy storage assembly and system wherein a plurality of fusion-type heat storage units are connected in parallel with a heat exchanger. To charge the units, solar or waste heat is fed into the heat exchanger where it is picked up by a heat transfer fluid which flows around cells in the respective units to sequentially melt substances in these cells and thereby store energy in the cells. To discharge the system, the heat transfer fluid is, again, pumped through the units and the heat exchanger to thereby pick up heat from substances in the cells (as they become frozen) which is taken out of the system at the heat exchanger.
A limitation of this prior-art system is that heat energy cannot be discharged from the system at several selected predetermined temperatures simultaneously. That is, the system only allows the extraction of one-temperature heat energy at a time. Thus, it is an object of this invention to provide a heat storage system which allows the discharge of heat at several temperatures simultaneously.
Another limitation of the above described system is that during periods when high temperature fluid is available from solar sources, or waste sources, one cannot necessarily store this energy at the high temperature in a high temperature unit. This is because heat may also be required to be simultaneously discharged from the system causing the total fluid temperature to be reduced. Thus, it is an object of this invention to provide a system which allows an available high temperature charging fluid to charge a high-temperature unit while simultaneously allowing another unit of the system to be discharged.
Still another limitation of the prior art was that the various heat storage assemblies could only be used with an external heat exchanger thus lowering the efficiency and increasing the expense of the system when only one heat storage assembly is used. It is therefore another object of this invention to provide a heat storage assembly which does not require an external heat exchanger for the charging and discharging thereof.
It is still another object of this invention to provide a heat storage assembly which can be used in a parallel system, or which can be used alone advantageously.
Finally, it is an object of this invention to provided a fusion-type heat storage assembly which can be economically manufactured and which is efficient in operation.